The presence of a specific proteolytic enzyme will be sought at the site of bone resorption from cholesteatomas induced in guinea pigs and from human cholesteatoma containing resorbing bone. Organ cultures of guinea pig wound tissue and of human skin will be used to obtain collagenase which will then be purified by salt fractionation and column chromatography. A specific antibody against the enzyme will be induced by injecting it into rabbits and isolating the antibody from rabbit serum. This antibody will be tagged and then incubated with a frozen section of cholesteatoma and bone enabling us to determine collagenase directly at the site of bone resorption in human and animal tissue. Further studies on the role of collagenase in bone resorption will be carried out by using bone sections as substrate for collagenase and other enzymes produced by cholesteatoma. Epidermal cysts will be induced in the middle ear of laboratory animals, in order to study the nature of the migrating squamous epithelium, the conditions leading to its ectopic position, and the mechanism by which it induces bone resorption. Several approaches will be used singly and in combination to produce cholesteatoma including induction of granuloma in the middle ear at the margin of the tympanic membrane, production of chronic perforations, middle ear suppuration, and eustachian tube blockage. The presence of induced cholesteatoma and determination of actual bone resorption will be determined histologically. BIBLIOGRAPHIC REFERENCES: Abramson, M., Asarch, R., and Litton, W. B.: "Experimental Aural Cholesteatoma Causing Bone Resorption", Ann. Otol., Rhinol., and Laryngol., 84:425-432, 1975. Huang, C.C., Abramson, M., Schilling, R.W., and Salome, R.: "Collagenase Activity in Tumors of the Head and Neck", Trans. Amer. Acad. Opthal. and Otol., 82:138-141, 1976.